Transforming growth factor beta (TGF-beta) is a multifunctional polypeptide, which was the first in an emerging super-family of regulatory polypeptides to be identified and purified to homogeneity. In our laboratory, TGF-beta is currently being isolated from human platelets. An alternate and abundant source of TGF-beta used by Collagen Corp. (Palo Alto, CA) is bovine bone. The amino acid sequence of human TGF-beta has been deduced from its cDNA sequence; however, only the first 30 N-terminal residues of the bovine homolog have been sequenced. One aim of the present study was to determine the complete amino acid sequence of bovine TGF-beta by cDNA cloning and sequencing. Interestingly, a second molecule, which shares about 70% amino acid sequence homology in the N- terminus with TGF-beta, has been isolated from bovine bone; this second form of TGF-beta is the most closely related member of the above-mentioned gene family. Isolation of a cDNA clone specific for the second form of TGF-beta would allow further characterization of its molecular nature and functional role. About five years have passed since the isolation of TGF-beta and its designation as a "transforming growth factor." However, the study of TGF-beta is no longer limited to that of its role in malignant transformation. Rather, its has become an increasingly expanding field which now encompasses growth modulation, differentiation, embryogenesis and wound repair. A second aspect of my work on TGF-beta involves a collaboration with Dr. Monique Dubois-Dalcq in the Laboratory of Molecular Genetics (NINCDS) designed to investigate the role of TGF-beta on growth and differentiation of glial cells of the vertebrate central nervous system (CNS).